Pyrometer tube



Jan. 23, 1940.

C. E. NOBLE PYROMETER TUBE Filed Dec. 22, 1957 ind/fw, 9/ nn/ Patented Jan. 23, 1940 nire sraas Arr PYROMETER TUBE poration of Illinois Application December 22, 1937, Serial No. 181,154

' 1 claim.

My invention relates to pyrometer tubes and has particular reference to a tube which is used for the protection of heat measuring apparatus in reducing and other furnaces. It is adapted primarily for the protection of thermocouples and to resist the breaking down effect of the penetrating or absorption action of gases which results from exposure of ordinary iron tubes to gases, leading to a breaking down ofthe structure of the tube and inaccurate measurement of the temperatures to Which these tubes are subjected, usually in cases running up to 1800 F. and higher.

Another and further object of my invention is the provision of a tube preferably composed of iron and at least 25% chromium, to which a thin layer of pure chromium is added by plating or otherwise, to make a hard, dense surface to the metal which is impervious to gases, which thoroughly closes any pin holes or surface pits in the tube, and which will not break down and deteriorate when subjected to extremely high temperatures.

Another and further object of my invention 25 is the provision of a tube which affords a resistance to the penetration and absorption of gases which are generated in the burning of high sulphur oils or high sulphur coals, and which cause a break down in structure of the tube and possibly results in absorption of these gases into the tube. in effect rendering the tube inaccurate in service and leading to the breaking down of the resistance of the thermocouple, resulting in inaccurate registering of temperatures.

' Another and further object of my invention is the provision of a tube of iron and composed of at least 27 to 35 percent chromium, to which is added a chromium coating by plating or the like, and which not only resists the action of the gases in high temperature reducing furnaces but also is longer in life than tubes of similar construction and which contain nickle, chromium or other alloys designed to resist the absorp tion of gases and which experiments Ahave proven will remain constant for at least four weeks in actual service, Whereas tubes made from iron, steel and other alloys have not shown a life greater than approximately one-third of the life 5o J(orf the tubes made in accordance with my inven- These and other objects of my invention will be more fully and better understood by reference to the accompanying sheet of drawings, and in which the single gure represents a tube (Cl. 13S-4) projecting through a wall or roof of a furnace, as may be desired.

Referring specifically to the drawing, a furnace wall is represented at I0. The body of the tube II is shown, composed preferably of iron 5 and from 27 to 35 percent chromium, to which on the outer surface a layer I2 of chromium is applied, (exaggerated as to thickness as shown in the drawing), this layer of chromium being applied by plating or any other approved method 10 whereby the chromium is evenly distributed over the entire outer surface of the tube II, of from one to ten hundred thousandths of an inch in thickness, thereby presenting a very hard, dense surface which is impervious to gases and the l5 like. A cap I3 is provided through which the usual thermocouple wires I4 and I5 pass by suitable connections, the cap I 3.being placed over the end of the tube I I, with the tube II being vinserted through a gland member I5, which is 20 the usual practice of inserting these pyrometer thermocouple tubes through the walls or roof of furnaces in order to measure the temperature in the furnace.

In carrying out the invention, a tube of appro- 25 priate size and form and closed at one of its ends is provided, composed of ordinary steel containing 27 to 35 percent chromium, the tube being made from a billet or seamless piece of steel, or being bored out of a block of material, all of a0 which is well known in the art. The tube is then placed as a cathode in an electrolytic cell containing an appropriate chromium electrolyte, and the outer surface is coveredlwith a layer of electro-deposited chromium of the desired thick- 35 ness. Prior to being placed in the chrome plating bath, the tube may be cleaned by being subjected to a proper alkali and acid dip, all of which is Well known in the art. A chromium coating I2 is therefore applied to the entire sur- 40 face of the tube by electroplating or any other suitable means by which a coating of chromium can be evenly distributed over the entire surface of the tube. The chromium plating forms a dense coating over the tube which, with the percentage of chromium contained in the tube, is fairly dense and offers high resistance to the penetration and absorption gases, but which by having the coating applied thereto has its resistance Aincreased very materially and which has its outer surface smooth and dense with all pin holes or surface pits filled up and protected from attack by the furnace gases.

The tubes may be removed from time to time, as may be desired, as they are used, and replaced u cumstances may suggest or render expedient Without departing from the spirit or scope of my invention.

I claim:

A pyrometer protecting tube composed of alloy steel containing from 27% to 35% chromium, said tube having an outer layer substantially impervious to gases comprising a coating of approximately pure chromium.

CHARLES E.v NOBLE.

CERTIFICATE OF CORRECTION.

Patent No. 2,187,9h9.

January 25, 19LLO.

CHARLES E. NOBLE.

It is hereby certified that the name of the assignee in the above numbered patent was erroneously written and printed as "Claud T. whereas said name should have been written Iand printed as Claud S. Gordon Companyof Chicago, 4Illinois, a corporation of' Illinois, as shown by the record of assignments in this office; and that the said Letters Patent should be read with this correction therein that the same may conform to the record of the case in the Patent Office.

Signed and sealed this 12th day of March, A. D. 1914.0.

(Seal) Henry Van Arsdale,

Acting Commissioner of Patents.

Gordon Company" CERTIFICATE OF CORRECTION Patent No. 2,187,9h9. January 25, 19h0.

cHABIns E. NOBLE.

It is hereby certified that the 'name of the assignee in the above numbered patent was erroneously written and printed as "Claud T. Gordon Company" whereas said name should have been written and printed as Claud S. Gordon Company,of Chicago, illinois, a -cerporation of Illinois, as shown by the record of assigrnnents in this office; and that the said Letters Patent should be read with this correction therein that the same may conform to the record of the case in the Patent Office.

Signed and sealed this 12th day of March, A. D. 19h0.

Henry Van Arsdale,

(Seal) W. Acting Commissioner of Patents. 

